[Loop Peeling] Enable peeling for loops with multiple exits

This CL enables peeling of the loop with multiple exits where
one exit should be from latch and others are basic blocks with
call to deopt.

The peeling is enabled under the flag which is false by default.

Reviewers: reames, mkuper, iajbar, fhahn
Reviewed By: reames
Subscribers: xbolva00, hiraditya, zzheng, llvm-commits
Differential Revision: https://reviews.llvm.org/D63923

llvm-svn: 366048

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 3212dec..e39ade5 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -402,7 +402,8 @@ LoopUnrollResult llvm::UnrollLoop(Loop *L, UnrollLoopOptions ULO, LoopInfo *LI,
     // counts. If we later unroll the loop, we want these to be updated.
     if (Peeled) {
       // According to our guards and profitability checks the only
-      // meaningful exit should be latch block.
+      // meaningful exit should be latch block. Other exits go to deopt,
+      // so we do not worry about them.
       BasicBlock *ExitingBlock = L->getLoopLatch();
       assert(ExitingBlock && "Loop without exiting block?");
       assert(L->isLoopExiting(ExitingBlock) && "Latch is not exiting?");